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Papers by Mariana Vaschetto
Current opinion in drug discovery & development, 2003
During the past few years, the introduction of ultra-high-throughput screening and new assay desi... more During the past few years, the introduction of ultra-high-throughput screening and new assay design and detection technologies has exponentially increased the amount and complexity of screening data. Effective use of this data implies a process that begins with assay design. An effective data management system should control a range of processes, from the initial selection of compounds and storage and mining of the assay result to more complex tasks, such as extracting patterns from these data. Remarkable advances have been made during the last year to increase efficiency at different phases of the screening, shifting the bottleneck of this process to data analysis. The challenge facing drug discovery today is to extract knowledge from these data. Knowledge discovery is defined as 'the non-trivial extraction of implicit, unknown, and potentially useful information from data'. A large amount of research is being devoted to optimize the extraction of knowledge from screening d...
The Journal of Physical Chemistry a, Sep 10, 1997
Recent Advances in Computational Chemistry, 2002
SUMMARY Our objective is to develop a fundamental understanding of the identity and character of ... more SUMMARY Our objective is to develop a fundamental understanding of the identity and character of nm-scale features (NFs) in nanostructured ferritic alloys (NFAs), especially at the smallest sizes. The NFs' features are believed to be responsible for the very high creep strength and radiation damage resistance of NFAs. Atom probe tomography studies have indicated that the NFs have Ti +
Journal of Molecular Structure-Theochem, 1999
In this work, we present an exhaustive study of the structural as well as the electronic properti... more In this work, we present an exhaustive study of the structural as well as the electronic properties of aniline obtained using several DFT based methods. The geometry of aniline obtained using the hybrid DFT methods (B3LYP, B3P86 and B3PW91) shows better agreement with the experimental values, than the methods containing the gradient corrected exchange functional (Becke 88). The new feature
Journal of Molecular Structure-Theochem, 1999
We present results of first-principles calculations of the electronic properties of several condu... more We present results of first-principles calculations of the electronic properties of several conducting polymers containing either phenylene or pyridine rings. The applied density functional method employs linear muffin-tin orbitals (LMTOs) as basis functions. It has been explicitly constructed for calculating the electronic properties of infinite, periodic, helical, polymeric chains. We study poly(p-phenylene) (PPP), poly(p-phenylenevinylene) (PPV), poly(2,5-pyridine) (PPy), poly(2,5-pyridinevinylene) (PPyV) and polyaniline (PANI). The structural parameters were obtained either from experimental information or by applying semi-empirical methods. We find that by replacing a carbon atom by a nitrogen atom in the phenylene ring, an occupied n-band appears. Simultaneously, the first ionization potential is increased which can be related to the electronegativity of nitrogen compared to that of carbon. When a vinylene linkage separates the rings, steric effects between the rings are diminished and the rings may thus be coplanar. This increases the p -electron delocalization and produces a stabilization of the system. In contrast, by replacing the vinylene linkage by an amine group (resulting in PANI) a non-planar polymer is obtained which has a larger band gap and a smaller ionization potential. ᭧ Journal of Molecular Structure (Theochem) 468 (1999) 181-191 0166-1280/99/$ -see front matter ᭧ Fig. 1. Schematic representation of the unit cell of the studied polymers.
The Journal of Physical Chemistry A, 1997
The Journal of Physical Chemistry A, 1999
The structural and electronic properties of pyridine, its oligomers, and polypyridine (PPY) as ob... more The structural and electronic properties of pyridine, its oligomers, and polypyridine (PPY) as obtained with density functional methods are presented in this work. Among the different exchange-correlation functionals used, B3LYP gives good structural results, whereas B3P88 predicts more accurately the electronic properties. The calculated first excitation energies of pyridine systems are in good agreement with experimental data. The coupling between the monomers in forming oligomers influences the structural and electronic properties of the system significantly. The trans head-to-head dimer is found to be the most stable form and the only one having a planar geometry. The introduction of a head-to-head or tail-to-tail coupling in order to break the regioregularity of a tetramer changes the frontier orbitals and the total energy of the system. The inclusion of a head-to-head coupling in the central units of a tetramer leads to a global stabilization of the system and lowers the HOMO, producing an increase in the first electronic excitation energy. Finally, the electronic properties of infinite PPY are obtained by extrapolations from those of finite oligomers. The calculated ionization potential, electronic affinity, and (π-π) 1 transition are 6.3, 3.4, and 2.9 eV, respectively, in excellent agreement with previous experimental reports. Furthermore, the band structures and density of states of PPY are calculated using a DFT-LMTO method. The calculated density of states is in good qualitative and quantitative agreement with experimental UPS spectrum for this system.
Synthetic Metals, 1999
Results of a theoretical study of the electronic properties of polymeric systems [M(CzX4)ln, with... more Results of a theoretical study of the electronic properties of polymeric systems [M(CzX4)ln, with M= Ni, 0.1, Zn and X= 0, S, Se, are presented. The calculations were carried through using a first-principles density-functional method (DFT-LMTO full-potential), We analyze the effects of varying the torsion angle between adjacent unit cells including its influence on the metal-ligand orbital overlap. The frontier orbitals depend strongly on the ligand, and the conductivity of the systems is predicted to be very dependent on the oxidation state of the metal (i.e., also on the presence of counterions). The Fermi level depends on X as well as on M.
Electroanalysis, 1998
Page 1. Catalytic Electrooxidation of 2-Mercaptoethanol on Perchlorinated Iron Phthalocyanine Ads... more Page 1. Catalytic Electrooxidation of 2-Mercaptoethanol on Perchlorinated Iron Phthalocyanine Adsorbed on a Graphite Electrode Marıa Jesús Aguirre,þ Mauricio Isaacs,þ Francisco Armijo,þ Nerilso Bocchi,þþ and José H. Zagal*þ ...
Current opinion in drug discovery & development, 2003
During the past few years, the introduction of ultra-high-throughput screening and new assay desi... more During the past few years, the introduction of ultra-high-throughput screening and new assay design and detection technologies has exponentially increased the amount and complexity of screening data. Effective use of this data implies a process that begins with assay design. An effective data management system should control a range of processes, from the initial selection of compounds and storage and mining of the assay result to more complex tasks, such as extracting patterns from these data. Remarkable advances have been made during the last year to increase efficiency at different phases of the screening, shifting the bottleneck of this process to data analysis. The challenge facing drug discovery today is to extract knowledge from these data. Knowledge discovery is defined as 'the non-trivial extraction of implicit, unknown, and potentially useful information from data'. A large amount of research is being devoted to optimize the extraction of knowledge from screening d...
The Journal of Physical Chemistry a, Sep 10, 1997
Recent Advances in Computational Chemistry, 2002
SUMMARY Our objective is to develop a fundamental understanding of the identity and character of ... more SUMMARY Our objective is to develop a fundamental understanding of the identity and character of nm-scale features (NFs) in nanostructured ferritic alloys (NFAs), especially at the smallest sizes. The NFs' features are believed to be responsible for the very high creep strength and radiation damage resistance of NFAs. Atom probe tomography studies have indicated that the NFs have Ti +
Journal of Molecular Structure-Theochem, 1999
In this work, we present an exhaustive study of the structural as well as the electronic properti... more In this work, we present an exhaustive study of the structural as well as the electronic properties of aniline obtained using several DFT based methods. The geometry of aniline obtained using the hybrid DFT methods (B3LYP, B3P86 and B3PW91) shows better agreement with the experimental values, than the methods containing the gradient corrected exchange functional (Becke 88). The new feature
Journal of Molecular Structure-Theochem, 1999
We present results of first-principles calculations of the electronic properties of several condu... more We present results of first-principles calculations of the electronic properties of several conducting polymers containing either phenylene or pyridine rings. The applied density functional method employs linear muffin-tin orbitals (LMTOs) as basis functions. It has been explicitly constructed for calculating the electronic properties of infinite, periodic, helical, polymeric chains. We study poly(p-phenylene) (PPP), poly(p-phenylenevinylene) (PPV), poly(2,5-pyridine) (PPy), poly(2,5-pyridinevinylene) (PPyV) and polyaniline (PANI). The structural parameters were obtained either from experimental information or by applying semi-empirical methods. We find that by replacing a carbon atom by a nitrogen atom in the phenylene ring, an occupied n-band appears. Simultaneously, the first ionization potential is increased which can be related to the electronegativity of nitrogen compared to that of carbon. When a vinylene linkage separates the rings, steric effects between the rings are diminished and the rings may thus be coplanar. This increases the p -electron delocalization and produces a stabilization of the system. In contrast, by replacing the vinylene linkage by an amine group (resulting in PANI) a non-planar polymer is obtained which has a larger band gap and a smaller ionization potential. ᭧ Journal of Molecular Structure (Theochem) 468 (1999) 181-191 0166-1280/99/$ -see front matter ᭧ Fig. 1. Schematic representation of the unit cell of the studied polymers.
The Journal of Physical Chemistry A, 1997
The Journal of Physical Chemistry A, 1999
The structural and electronic properties of pyridine, its oligomers, and polypyridine (PPY) as ob... more The structural and electronic properties of pyridine, its oligomers, and polypyridine (PPY) as obtained with density functional methods are presented in this work. Among the different exchange-correlation functionals used, B3LYP gives good structural results, whereas B3P88 predicts more accurately the electronic properties. The calculated first excitation energies of pyridine systems are in good agreement with experimental data. The coupling between the monomers in forming oligomers influences the structural and electronic properties of the system significantly. The trans head-to-head dimer is found to be the most stable form and the only one having a planar geometry. The introduction of a head-to-head or tail-to-tail coupling in order to break the regioregularity of a tetramer changes the frontier orbitals and the total energy of the system. The inclusion of a head-to-head coupling in the central units of a tetramer leads to a global stabilization of the system and lowers the HOMO, producing an increase in the first electronic excitation energy. Finally, the electronic properties of infinite PPY are obtained by extrapolations from those of finite oligomers. The calculated ionization potential, electronic affinity, and (π-π) 1 transition are 6.3, 3.4, and 2.9 eV, respectively, in excellent agreement with previous experimental reports. Furthermore, the band structures and density of states of PPY are calculated using a DFT-LMTO method. The calculated density of states is in good qualitative and quantitative agreement with experimental UPS spectrum for this system.
Synthetic Metals, 1999
Results of a theoretical study of the electronic properties of polymeric systems [M(CzX4)ln, with... more Results of a theoretical study of the electronic properties of polymeric systems [M(CzX4)ln, with M= Ni, 0.1, Zn and X= 0, S, Se, are presented. The calculations were carried through using a first-principles density-functional method (DFT-LMTO full-potential), We analyze the effects of varying the torsion angle between adjacent unit cells including its influence on the metal-ligand orbital overlap. The frontier orbitals depend strongly on the ligand, and the conductivity of the systems is predicted to be very dependent on the oxidation state of the metal (i.e., also on the presence of counterions). The Fermi level depends on X as well as on M.
Electroanalysis, 1998
Page 1. Catalytic Electrooxidation of 2-Mercaptoethanol on Perchlorinated Iron Phthalocyanine Ads... more Page 1. Catalytic Electrooxidation of 2-Mercaptoethanol on Perchlorinated Iron Phthalocyanine Adsorbed on a Graphite Electrode Marıa Jesús Aguirre,þ Mauricio Isaacs,þ Francisco Armijo,þ Nerilso Bocchi,þþ and José H. Zagal*þ ...